The present invention relates to a new and improved filter assembly which is advantageously utilized in association with an apparatus which electrolytically removes material from a workpiece.
A known apparatus for electrolytically removing material from a workpiece is disclosed in U.S. Pat. No. 3,793,170 to James D. Andrews. This apparatus includes a direct current power source to establish an electrical potential between an electrode wire and a workpiece. A plurality of nozzles direct a flow of electrolyte agains the workpiece. Other known devices for electrolytically removing material from a workpiece by directing a flow of electrolyte toward a workpiece through one or more nozzles are disclosed in U.S. Pat. Nos. 3,188,284 and 3,846,262.
The maintaining of a predetermined electrolyte flow and pressure is critical to the accuracy with which the workpiece is shaped during the electrolytic removal of material. This is particularly true in hole drilling techniques in which a stationary nozzle directs a high pressure flow of electrolyte against a workpiece to drill a hole which may be as small as 0.004 inches in diameter. In order to accomplish the forming of a hole of a relatively small diameter, the nozzle must have a minimum inside diameter which is at least as small as the inside diameter of the hole.
For economic reasons, after the electrolyte has been directed against the workpiece, it is collected and returned to a reservoir and subsequently reused in a manner which may be similar to that disclosed in U.S. Pat. Nos. 3,441,493; 3,574,082 and 3,658,682. Since a nozzle which directs the electrolyte against the workpiece tapers to a very small minimum inside diameter, it is necessary to remove from the electrolyte any particles of dirt or other contaminants which would block or even partially block the flow of electrolyte from the nozzle. In order to prevent this from happening, it has been a common practice to utilize a barrier type filter. However, it has been found that barrier type filters gradually become filled up with contaminants and reduce the electrolyte flow and pressure unless they are removed and cleaned. Although backflushing these barrier type filters may improve the flow through the filters, the backflushing time takes away from the machine operating time and is not entirely satisfactorily.
In addition to the barrier type filters commonly utilized in association with apparatus for electrolytically removing material from a workpiece, other known filters have been utilized for various purposes. Some of these known filters are disclosed in U.S. Pat. Nos. 427,906; 902,349; 3,485,374; 3,579,441; and 3,953,334.